The Viceroy of India during Mahatma Gandhi's Dandi March (Salt Satyagraha) was:

Lord Irwin (Edward Wood, later Lord Halifax) was the Viceroy of India from 1926 to 1931, during which Gandhi led the Dandi March (Salt Satyagraha) in 1930.

About the Dandi March:

• Gandhi chose salt as the symbol of protest, because the salt tax affected every Indian, rich or poor.
• Before the march, Gandhi wrote a letter to Irwin, listing eleven demands, including the abolition of the salt tax; when there was no response, he began the march.
• He walked with 78 followers from the Sabarmati Ashram to Dandi, on the coast of Gujarat.
• He broke the salt law by making salt from sea water at Dandi on 6 April 1930.
• This began the Civil Disobedience Movement across India.

About Lord Irwin:

He was a British Conservative politician, and later became Foreign Secretary (as Lord Halifax).

Important events of his time:

• The Simon Commission arrived in India and was boycotted, with the slogan "Simon Go Back".
• The Bardoli Satyagraha (1928) led by Sardar Patel.
• The Nehru Report (1928).
• The "Deepavali Declaration" (October 1929), in which Irwin announced that Dominion Status was the natural goal of India's constitutional progress.
• The Lahore session of the Congress (December 1929), which adopted the goal of Purna Swaraj (complete independence).
• The Civil Disobedience Movement.
• The First Round Table Conference in London.
• The Gandhi-Irwin Pact, under which Gandhi agreed to suspend the Civil Disobedience Movement and attend the Round Table Conference, and the government agreed to release political prisoners.
• Bhagat Singh and Batukeshwar Dutt threw bombs in the Central Legislative Assembly (April 1929).

Why not the other options?

• ✗Lord Reading was his predecessor.
• ✗Lord Willingdon succeeded him.
• ✗Lord Linlithgow was a later Viceroy.